1. Field of the Invention
The present invention relates to a compression ring used for internal combustion engines and compressors, and a method for manufacturing the same.
2. Description of the Related Art
Recently, nitriding has been applied to a compression ring. Nitriding is carried out by gas nitriding or salt-bath nitriding. According to these methods, not only an outer peripheral surface but also upper and lower surfaces and an inner peripheral surface become nitrided.
As described above, the whole peripheral portion of the ring becomes nitrided. Therefore, when a thick nitriding is applied to a ring which is thin in width and provided with both ends having notches, a notched portion having a small sectional area in each end increases against brittleness, decreases against strength, and possibly breaks from that portion. Because of this, it is not possible to meet the demands of implementation of thin-width and high wear resistance of the ring.